The present invention is related to Japanese patent application No. Hei. 2000-159684, filed May 30, 2000; the contents of which are incorporated herein by reference.
The present invention relates to a valve apparatus, and more particularly, the present invention relates to a valve apparatus used in a fuel injection system of an internal combustion engine such as a diesel or gasoline engine or the like.
A valve apparatus used for controlling flow-in and flow-out of fuel such as a spill valve, a flow control valve or the like of a fuel injection pump, generally cuts a fuel flow path by sliding and seating a valve member on a tapered seat portion in a valve body. However, unlike lubricant, fuel is devoid of lubricity, and accordingly, by repeatedly opening and closing thereof there is the possibility of seizure or wear of the valve member or seat portion. Hence, in conventional sliding valve member members, seizure and wear resistant material is used. For example, a quenched and tempered material of SKH51 may be used. In a valve body having a seat, and in which the shape is complicated, a carburized material of SCr415 having excellent workability is used.
The quenched and tempered material of SKH51 comprising the valve member is very hard steel in which hard particles are dispersed in a matrix. It very effectively prevents valve member wear. However, depending on the construction, during low speed high load operation in which lubricity deteriorates, the seat portion (which is a counterpart member) is worn. For example, the drawback is caused when rotational movement of the valve member is not restricted and the valve member repeatedly impinges the seat portion from the vertical direction and slips in the rotational direction during valve closing. To counter this, the valve body material may be interchanged with a higher hardness material. However, since the workability of the valve body is deteriorated with harder material, the cost is increased.
Hence, the present inventors have reinvestigated the material used in a valve apparatus for controlling flow-in and flow-out of a fluid having low lubricity, as in a fuel injection system.
In light of these and other drawbacks, the present invention provides a valve apparatus in which seizure, wear or the like is not caused in a valve member or a valve body and for which fabrication and workability remains good. As such, a valve body is constructed of steel having a martensitic structure. The valve member for opening and closing a fluid flow path by sliding in the valve body is constructed of steel in which hard particles are dispersed in a matrix having the martensitic structures, and a difference in hardness (Hv: Vickers hardness) between the matrix and the hard particles is preferably equal to or smaller than 1000.
Conventional valve body wear is caused when the valve member is moved vertically and impinges on the seat portion. The matrix of the quenched and tempered material of SKH51 constituting the valve member is deformed or worn. As a result, coarse hard particles float up and grind the seat portion. In contrast thereto, according to the valve member of the present invention, a difference in hardness between the matrix and the hard particle is as small as Hv: 1000 or smaller and accordingly, deformation or wear by impingement is reduced. Therefore, the valve member hardness is made high by dispersing hard particles therein. Further, hard particles are prevented from projecting from the surface and grinding the valve body. Further, by making the valve body with the hard martensitic structure, sufficient hardness is provided. Hard particles are not included and accordingly, workability is excellent.
In another aspect, carbide particles having an average particle diameter equal to or smaller than 3 xcexcm are used. When the average particle diameter is small, the hard particle is difficult to project or detach. Further, grinding of the counterpart member by exposed hard particles and wear is reduced.
In another aspect, the valve body is constructed of a carburized material of low carbon alloy steel or a carburized nitride material of low carbon steel and the valve member is constructed of a quenched and tempered material of high carbon chromium steel. For the carburized material of low carbon alloy steel constituting the valve body, there is a carburized material SCr415 or a carburized material of SCM420 and as a carburized nitride material of low carbon steel, there is a carburized nitride material of S10C. Further, for the quenched and tempered material of high carbon chromium steel constituting the valve member, there is a quenched and tempered material of SUJ1 or a quenched and tempered material of SUJ2.
In another aspect, the valve body includes a guide hole in which the valve member slides and a seat portion seated with the valve member for cutting the fluid flow path.
In another aspect, the valve member is driven electrically by a drive unit. As such, when closing the valve, impact received by the valve body may become large. Therefore, the advantages of the present invention become very much realized here.
In another aspect, the valve apparatus controls flow-in and flow-out of fuel in a fuel injection system. Generally, since fuel is devoid of lubricity, seizure or wear is liable to be caused and therefore, the effect of applying the present invention is enormous. Specifically, when the valve apparatus is used for a spill valve of a distribution type fuel pump, seizure or wear is prevented and the durability can be promoted significantly.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.